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We report spatiotemporal evolution of emission and absorption signatures of Al species in a nanosecond (ns) laser-produced plasma (LPP). The plasmas were generated from an Inconel target, which contained ∼ 0.4 wt. % Al, using 1064 nm, ≈ 6 ns full width half maximum pulses from an Nd:YAG laser at an Ar cover gas pressure of ≈ 34 Torr. The temporal distributions of the Al I (394.4 nm) transition were collected from various spatial points within the plasma employing time-of-flight (TOF) emission and laser absorption spectroscopy, and they provide kinetics of the excited state and ground state population of the selected transition. The emission and absorption signatures showed multiple peaks in their temporal profiles, although they appeared at different spatial locations and times after the plasma onset. The absorption temporal profiles showed an early time signature representing shock wave propagation into the ambient gas. We also used emission and absorption spectral features for measuring various physical properties of the plasma. The absorption spectral profiles are utilized for measuring linewidths, column density, and kinetic temperature, while emission spectra were used to measure excitation temperature. A comparison between excitation and kinetic temperature was made at various spatial points in the plasma. Our results highlight that the TOF measurements provide a resourceful tool for showing the spatiotemporal LPP dynamics with higher spatial and temporal resolution than is possible with spectral measurements but are difficult to interpret without additional information on excitation temperatures and linewidths. The combination of absorption and emission TOF and spectral measurements thus provides a more complete picture of LPP spatiotemporal dynamics than is possible using any one technique alone. [ABSTRACT FROM AUTHOR]

This paper deals with double-pulse laser-induced breakdown spectroscopy (LIBS) underwater, which is a promising analytical method for elemental analysis in the deep sea up to a water depth of 6000 m. A double-pulse laser with a wavelength of 1064 nm is used, which provides a pulse energy of up to 266 mJ for each laser pulse (in single pulse mode), a pulse width of 5–7 ns and a pulse delay in the range of 0.5 to 20 µs. In the double-pulse LIBS method, the first laser pulse creates a cavity on the material surface, and then the second laser pulse forms the plasma in this cavity. It is expected that the plasma is affected by the cavity's size and lifetime. For this reason, the influence of focus position, pulse energy and pulse delay on the cavity and plasma formation at shallow water depth has been investigated. [ABSTRACT FROM AUTHOR]

Low-pressure plasma processes are routinely used to grow, functionalize or etch materials, and thanks to some of its unique attributes, plasma has become a major player for some applications such as microelectronics. Plasma processes are however still at a research level when it comes to the synthesis and functionalization of nanoparticles. Yet plasma processes can offer a particularly suitable solution to produce nanoparticles having very peculiar features since they enable to: (i) reach particle with a variety of chemical compositions, (ii) tune the size and density of the particle cloud by acting on the transport dynamics of neutral or charged particles through a convenient setting of the thermal gradients or the electric field topology in the reactor chamber and (iii) manipulate nanoparticles and deposit them directly onto a substrate, or codeposit them along with a continuous film to produce nanocomposites or (iv) use them as a template to produce 1D materials. In this article, we present an experimental investigation of nanoparticles synthesis and dynamics in low-pressure microwave plasmas by combining time-resolved and in-situ laser extinction and scattering diagnostics, QCL absorption spectroscopy, mass spectrometry, optical emission spectroscopy and SEM along with a particle transport model. We showed for the first time the thermophoresis-driven dynamic of particle cloud in electrodless microwave plasmas. We showed that this effect is linked to particular fluctuations in the plasma composition and results in the formation of a void region in the bulk of the plasma surrounded by a particle cloud in the peripherical post-discharge. We also reveals and analyze the kinetics of precursor dissociation and molecular growth that result in the observed nanoparticle nucleation. [ABSTRACT FROM AUTHOR]

This study delves into the intricate dynamics of laser-induced damage in fused silica using a time-resolved pump-probe (TRPP) shadowgraph. Three typical ultra-fast processes, laser-induced plasma evolution, shockwave propagation and material fracture splashing, were quantitatively investigated. The results indicate that the diameter of plasma is proportional to the pulse laser energy and increases linearly during the pulse laser duration with an expansion rate of approximately 6 km/s. The maximum shockwave velocity on the air side is 9 km/s, occurring at the end of the pulse duration, and then rapidly decreases due to air resistance, reaching approximately 1 km/s around a 300 ns delay. After hundreds of nanoseconds, there is a distinct particle splashing phenomenon, with the splashing particle speed distribution ranging from 0.15 km/s to 2.0 km/s. The particle sizes of the splashing particles range from 4 μm to 15 μm. Additionally, the smaller the delay, the faster the speed of the splashing particles. Overall, TRPP technology provides crucial insights into the temporal evolution of laser-induced damage in fused silica, contributing to a comprehensive understanding essential for optimizing the performance and safety of laser systems. [ABSTRACT FROM AUTHOR]

In this paper, an analytical formalism is developed for electron acceleration using two crossed and identical laser pulses in a plasma channel. The net electron energy is increased and the electron diffraction is decreased through the utilization of radially polarized (RP) crossed-focused laser pulses. The study investigates the impact of various parameters, such as laser amplitude, ion density, initial kinetic energy, injection angle, laser pulse duration, and spot size on electron energy gain within a preformed plasma ion channel. The presence of space-charge field confines the dynamic of electrons along the longitudinal direction. Consequently, the transverse component of the laser pulse vanishes along the propagation axis, whereas the longitudinal component provides a longitudinal force. This configuration leads to the observation of gain in energy of electrons in GeV at a laser intensity ∼ 10 19 W / cm 2 where the ion density is ∼ 10 23 m - 3 in plasma channel. [ABSTRACT FROM AUTHOR]

For CdZnTe crystals containing extended defects – coherent and incoherent twin boundaries, as well as lamellar systems of twins, we measure the propagation patterns of surface acoustic waves (SAW) in the gigahertz range excited by a sharply focused femtosecond laser pulse. Comparison of the calculated SAW radial velocities with experimental data allows us to determine the local crystallographic orientation of crystal regions with defects. We discover strong anisotropic scattering of SAW at twin boundaries and show that the structure of the twin boundary can be determined from the pattern of SAW scattering. Also, we demonstrate the non-reciprocal SAW propagation in lamellar twin systems, as well as quasi-waveguide SAW propagation along the lamellar twin layer. [ABSTRACT FROM AUTHOR]

A stand is described that is designed to study the emission properties of laser plasma in the extreme ultraviolet range (EUV) formed on liquid jet targets. To form a jet target, a pulse valve and capillaries of various diameters are used. A Nd:YAG laser is used (with a wavelength of 1064 nm, a pulse duration of 11 ns, a frequency of up to 10 Hz, and a pulse energy of 500 mJ) to excite laser plasma. To investigate the emission spectra, a mirror X-ray spectrometer calibrated in absolute units, an Aurora 4000 visible-range spectrometer, and a microscope operating in the EUV range are used. Photographing of the formed liquid jets is also provided. The design of the stand and its main parameters are presented. The results of the first experiments to study the processes of liquid outflow from various nozzles into vacuum are also presented. [ABSTRACT FROM AUTHOR]

Measurement of the temporal evolution of laser-produced plasma temperature is very important for many of its applications, and several plasma diagnostic tools are routinely used by researchers. However, it is very challenging to measure the properties of the plasma at the early and late times of its evolution using a single diagnostic tool. In this study, we combined emission and laser absorption spectroscopy to compare the excitation temperatures of a laser-produced uranium plasma system. Several U I transitions in the near-infrared spectral range (775–800 nm) were considered, and the Boltzmann plot method was used to measure the excitation temperatures using both emission and absorption spectroscopy. Emission spectroscopy provided early-time temperature measurements of the plasma up to times 2–20 µs, while absorption spectroscopy provided temperature measurements at late times of plasma evolution (for times 5–80 µs). The emission and absorbance of U I transitions were found to follow the Boltzmann distribution, indicating the plasma is likely in the state of local thermodynamic equilibrium even at late times of its lifetime. The emission and absorption-based time-resolved excitation temperatures demonstrated good agreement at earlier times (≤15 µs) in the overlapped temporal region, while a deviation in the measured values was seen at times (≥15 µs), and potential reasons for such a disagreement are discussed. [ABSTRACT FROM AUTHOR]

We report on a study of laser plasma instabilities with 527 nm laser pulses in an intensity range of 0.5 × 10 13 − 1.1 × 10 15 W cm − 2 and plasma parameters entering a regime that is relevant for direct drive inertial confinement fusion. Using the kilojoule high repetition rate L4n laser at the Extreme Light Infrastructure—Beamlines, more than 1300 shots were collected, and the onset and the growth of stimulated Brioullin scattering (SBS) and stimulated Raman scattering (SRS) were studied with a high confidence level. The measured onset intensities are 0.2 × 10 14 W cm − 2 for SBS and 1.4 × 10 14 W cm − 2 for SRS. At the maximum intensity, the total fraction of backscattered energy reaches 2.5% for SBS and 0.1% for SRS. These results are of high relevance for advanced concepts for inertial fusion energy, which rely on the use of 527 nm laser light to drive the implosion of the fuel target, and in particular, they can be used as a benchmark for advanced simulations. [ABSTRACT FROM AUTHOR]

We demonstrated spectral control of beyond extreme ultraviolet (B-EUV) emission at a central wavelength of 6.76 nm from a gadolinium (Gd) laser-produced plasma. The highest spectral purity (SP) was 5.1% under dual 1-μm laser pulse irradiation. It doubled compared to a value of 2.4% attained under single laser pulse irradiation of solid density Gd because of the reduction in optical depth. The highest maximum SP was higher than that obtained using a mid-infrared laser at 10.6 μm. The SP for the 150-ps main laser was also higher than that for 6-ns main laser irradiation. Our approach can be extended to mid-infrared solid-state laser-produced plasmas (LPPs) using driving laser wavelengths ranging from 2 to 9 μm for efficient B-EUV source development. [ABSTRACT FROM AUTHOR]

Polymer-based membranes represent an irreplaceable group of materials that can be applied in a wide range of key industrial areas, from packaging to high-end technologies. Increased selectivity to transport properties or the possibility of controlling membrane permeability by external stimuli represents a key issue in current material research. In this work, we present an unconventional approach with the introduction of silver nanoparticles (AgNPs) into membrane pores, by immobilising them onto the surface of polyethyleneterephthalate (PET) foil with subsequent physical modification by means of laser and plasma radiation prior to membrane preparation. Our results showed that the surface characteristics of AgNP-decorated PET (surface morphology, AgNP content, and depth profile) affected the distribution and concentration of AgNPs in subsequent ion-track membranes. We believe that the presented approach affecting the redistribution of AgNPs in the polymer volume may open up new possibilities for the preparation of metal nanoparticle-filled polymeric membranes. The presence of AgNPs on the pore walls can facilitate the grafting of stimuli-responsive molecules onto these active sites and may contribute to the development of intelligent membranes with controllable transport properties. [ABSTRACT FROM AUTHOR]

Laser-assisted discharge-produced plasma (LDP) is one of the ways to generate extreme ultraviolet (EUV) light used in the semiconductor manufacturing processes. This light source uses a pulsed laser and a high-current pulsed electrical discharge to make a high-temperature and high-density tin plasma. One of two rotating disk electrodes, of which surfaces are coated by liquid tin (Sn), is irradiated by the laser to produce tin plasma. The plasma propagates from one electrode (cathode) to the other (anode) and ignites an electrical breakdown between the electrodes. The low-inductance circuit connected to the electrodes provides a current of approximately 15 kA and 150 ns to the tin plasma. The plasma implodes due to its own magnetic pressure, and EUV radiation is emitted from the resultant hot and dense plasma. High-speed ions are also emitted from the plasma and limit the lifetime of the mirror used to collect the EUV light. We need to maximize the light emission and minimize the ion emission. The role of the laser is essential in the LDP EUV source not only to ignite the discharge but also to condition the initial plasma. It influences EUV energy, EUV brightness, and emitted ion speed distribution of the plasma. The experiment suggested that laser intensity higher than 25 GW/cm2 produced high EUV brightness and low emitted ion speed. [ABSTRACT FROM AUTHOR]

To solve such global problems as climate stabilization and reducing greenhouse gas luminescences requires an integrated approach, including a strategic analysis of the problem and the development of criteria for selecting proposed solutions, a natural scientific research on the possibilities and ways to implement the assigned tasks, as well as an economic justification for the feasibility of implementing the developed measures. The present publication is an attempt to apply this approach to the problem of hydrogen energy via proposing the production of hydrogen by pyrolysis of natural gas in laser plasma as one of the ways to its solution. Therewith, the main attention is focused on the chemical processes that occur in laser plasma, as well as on the nature of the transformations that occur in the solid pyrolysis product. [ABSTRACT FROM AUTHOR]

Theoretical investigation on self-focusing of an elliptical q-Gaussian laser beam, carrying an intensity ripple over its cross section, in plasma with an axial density ramp has been presented. The optical nonlinearity of plasma has been modeled by the relativistic mass nonlinearity of plasma electrons in the field of a laser beam. Using the variational theory approach, semi-analytical solutions of the wave equations for the fields of the main beam and that of the ripple have been obtained. Emphasis has been put on the evolutions of the beam widths of the main beam and that of the ripple. [ABSTRACT FROM AUTHOR]

Liquid aluminum containing the important alloying element magnesium in varying concentrations was analyzed using in-situ laser-induced breakdown spectroscopy (LIBS). Magnesium emission shows an exponential dependence on melt temperature that correlates well with the expected partial pressure of magnesium above the aluminum melt. Furthermore, comparison with LIBS measurements on corresponding solid samples supports the conclusion that a significant part of Mg emission from liquid metal samples originates from the vapor phase above the metal surface. Simultaneously, curves of growth measured over four orders of magnitude in Mg concentration reveal a level of self-absorption for liquid aluminum samples that is stronger than for solid aluminum samples having a corresponding Mg concentration, and beyond what is expected from conventional plasma models. The implications for measurements of volatile species in liquid metals in general are discussed. Graphical abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

We present the development of an experimental platform that can collect four frames of x-ray diffraction data along a single line of sight during laser-driven, dynamic-compression experiments at the National Ignition Facility. The platform is comprised of a diagnostic imager built around ultrafast sensors with a 2-ns integration time, a custom target assembly that serves also to shield the imager, and a 10-ns duration, quasi-monochromatic x-ray source produced by laser-generated plasma. We demonstrate the performance with diffraction data for Pb ramp compressed to 150 GPa and illuminated by a Ge x-ray source that produces ∼7 × 1011, 10.25-keV photons/ns at the 400 μm diameter sample. [ABSTRACT FROM AUTHOR]

The theory of the terahertz (THz) waves emission from a near-critical plasma slab under the action of the focused p -polarized laser pulse is developed. The spectral, angular and energy characteristics of the THz signal are studied as functions of the focusing degree and the incidence angle of laser radiation, as well as the density and thickness of the plasma slab. It is shown that the extremely strong increase in the energy of the THz signal (up to millijoule level) and conversion rate (up to 10 %) occurs at the almost normal incidence of the ultra-short, tightly focused p -polarized laser pulse on the thin plasma slab with the near-critical density and rare electron collisions. [ABSTRACT FROM AUTHOR]

A numerical model was designed and implemented to investigate the influence of plasma defocusing on laser characteristics. The effects of plasma defocusing were investigated by studying beam divergence, intensity reduction, and blue shifting. The diffusion of the ultra-intense laser beam in gas cells was within a Rayleigh range. Moreover, using dual-gas-cells, the impact of quasiphase matching (QPM) on the creation of harmonic pulses in argon and hydrogen plasmas was studied. The alternating structure of argon and hydrogen gas cells showed a perfect build-up of the generated ultra-short harmonics pulses. The impact of electron density on laser diffusion and the creation of harmonic pulses were also investigated in this work. In the simulation, argon plasma with different plasma densities was used in an alternating structure to create dual-gas-cells and quasi-phase-matching. Noticeable conversion of the fundamental laser pulses to harmonics pulses was accomplished in the model by using the QPM concept [ABSTRACT FROM AUTHOR]

Laser drilling is not only widely used in a variety of materials but also commonly applied to diverse industrial fields. Due to the fast processing speed, the monitoring of the laser drilling process has always been a challenge. Some studies have been conducted to measure the signal of laser-induced plasma in the laser percussion drilling process by applying an external electric field to monitor the laser percussion drilling process in real-time. Using the laser-induced plasma signal for monitoring purposes, the relationship model between the measured plasma signal and the hole size achieved with laser percussion drilling has not been established. Once the relationship model is determined, the plasma signal can be used to predict the size of the laser drilled hole dimensions in real-time, and further realize a closed-loop control of the laser processing for a higher control technology. For this reason, we conducted a series of laser percussion drilling experiments with a fibre laser on 304 stainless steel and established a model by curve fitting with the laser percussion drilled hole sizes and the plasma signals in various laser processing parameters. [ABSTRACT FROM AUTHOR]

The formation of laser-induced plasma on a solid target depends strongly on the laser pulse parameters and the ambient conditions. In this work, the characteristics of laser-induced plasma generated in water and in air were investigated with two laser pulse durations of 6 ns and 17 ns. It was shown that the responses of laser-induced breakdown spectroscopy (LIBS) signals on the laser pulse duration in water and in air are different. In water, the 17 ns laser induces a brighter plasma and a stronger LIBS signal, whereas in air, the 6 ns laser is better. Such differences were attributed to the different plasma growth mechanisms in water and in air. The plasma growth in air is driven by strong laser-supported absorption waves, where the 6 ns laser with a higher peak irradiance corresponds to a stronger shock wave and more efficient heating on the plasma. Whereas for plasma growth in water, a great amount of laser energy is consumed in the material phase transitions, and in the mechanical effects of bubble expansion and shock wave propagation. The underwater plasma is far less heated by the laser pulse, and more easily suffers from the multiple breakdowns of water producing multiple shock waves and multi-plasmas. By using a longer laser pulse, which has a lower peak irradiance, the underwater plasma can absorb more laser energy over a longer laser pulse duration, and the multiple breakdown phenomenon can be suppressed. This results in a higher quality of underwater LIBS signals. The present work gives insights into the mechanism of plasma growth in water and in air, and provides suggestions for the choice of laser pulses in the relevant LIBS analyses. [ABSTRACT FROM AUTHOR]

It is indispensable to accurately and sensitively identify and analyze the elemental composition of human blood serum. In the current study, human blood serums were analyzed for elements utilizing orthogonal dual pulse laser-induced breakdown spectroscopy (DP-LIBS) setup in He gas environment. Experimentally, a fundamental pulse Nd:YAG laser (1064 nm, 7 ns) was irradiated just above the material target to induce a luminous gas plasma. A third harmonic pulse Nd:YAG laser (355 nm, 7 ns) was subsequently focused on the material surface to initiate a target plasma to ablate the atoms from the blood serum film to be sent to the gas plasma region. Double pulse LIBS technique has been successfully applied to increase the LIBS signal intensity up to 8 folds of major, minor, and trace components in human blood serum. Furthermore, a number of emission lines that were indistinctly detected by single pulse LIBS were accurately identified with the use of the DP-LIBS. A variety of components from the human blood serum have been analyzed both qualitatively and quantitatively. Element concentrations measured in human blood are to be 8360 ppm, 219 ppm, 581 ppm, 785 ppm, 343 ppm, 293 ppm, and 12 ppm for C, Ca, K, Mg, P, Na, and Fe, respectively. The LIBS outcome results are in excellent agreement with the results acquired by applying the standard XRF technique. [ABSTRACT FROM AUTHOR]

Er3+-ions doped SiO2-ZnO-Na2O thin films were fabricated using ultrafast laser plasma doping (ULPD) techniques under different ambient atmospheres; vacuum, nitrogen, oxygen and argon gas. The thickness of the layer produced depends on the ambient atmosphere during fabrication. The layer fabricated under a vacuum is the thinnest among all of the samples. In addition, the surface layer for the sample fabricated under a vacuum environment seems to be relatively smoother compared with those of the others. XRD patterns show that all samples are in a mixed amorphous-crystalline phase. All the Raman spectra exhibited a similar pattern, except for the intensity of the Si peak which depended on the thickness of the obtained layer. The PL intensity for each sample corresponds to the amount of Er3+ ions embedded in the doped layer. However, all samples still exhibited silicate-based characteristics, indicating nitrogen in Si3N4 was lost in the form of nitrogen gas during fabrication. [ABSTRACT FROM AUTHOR]

In this review, we attempt to provide a brief account of laser-induced breakdown spectroscopy (LIBS) methodology and technological developments. We also summarize various methods adopted for exploiting LIBS. Besides, a brief overview of combination of LIBS in conjunction with other methods is also given. [ABSTRACT FROM AUTHOR]

In this work, we investigate the properties of the plasma induced by focusing a high-power laser beam on an aluminum target that was cooled by a helium refrigerator from room temperature down to 20 K. Fast, streak photographs of the plasma were taken at different temperatures and laser energies. From the images obtained, position-vs-time plots were made for each experiment, and from them, the speed was calculated. Additionally, narrowband interference filters were employed to image the dynamics of ions and neutrals separately. It was found that the plasma plume has two distinct speeds: that of its center and that of the outer edge. For unfiltered images, the former has values within the interval 6.2 to 9.1 km/s, while the latter can reach speeds of the order of hundreds of km/s. It was found that the plume of a target cooled to 20 K has a length that is 8%–12% less than the corresponding size at room temperature. Chilling the target did not seem to affect significantly either the plume's speed of expansion or the size of the crater produced. Lower bounds were estimated for the momentum imparted to the ejecta and the specific impulse. The latter can reach a 920-s level, nearly twice as much the amount obtained with chemical rocket fuel. [ABSTRACT FROM AUTHOR]

We present an experimental and simulation-based investigation of the temporal evolution of light emission from a thin, laser-ionized helium plasma source. We demonstrate an analytic model to calculate the approximate scaling of the time-integrated, on-axis light emission with the initial plasma density and temperature, supported by the experiment, which enhances the understanding of plasma light measurement for plasma wakefield accelerator (PWFA) plasma sources. Our model simulates the plasma density and temperature using a split-step Fourier code and a particle-in-cell code. A fluid simulation is then used to model the plasma and neutral density, and the electron temperature as a function of time and position. We then show the numerical results of the space-and-time-resolved light emission and that collisional excitation is the dominant source of light emission. We validate our model by measuring the light emitted by a laser-ionized plasma using a novel statistical method capable of resolving the nanosecond-scale temporal dynamics of the plasma light using a cost-effective camera with microsecond-scale timing jitter. This method is ideal for deployment in the high radiation environment of a particle accelerator that precludes the use of expensive nanosecond-gated cameras. Our results show that our models can effectively simulate the dynamics of a thin, laser-ionized plasma source. In addition, this work provides a detailed understanding of the plasma light measurement, which is one of the few diagnostic signals available for the direct measurement of PWFA plasma sources. [ABSTRACT FROM AUTHOR]

An investigation was conducted into two colliding laser-produced plasmas collimated by two face-to-face channels, which makes the plasmas close to one-dimensional (1-D) and thus easier to simulate. The study was carried out using time-resolved imaging, and a 1-D fluid-descriptive model with the ambipolar electric field and collisional coupling taken into account. The time-resolved images show that the 1-D colliding plasmas follow a division into three distinct periods, namely, pre-colliding, colliding, and finally the stagnation layer dissipating. In the pre-colliding period, there is no plasma coming out of the channels, but illumination features are observed near the inner surfaces of the two blocks for more than 150 ns, which is much longer than the laser pulse duration. In the colliding period, there is continuous ejection of plasma from the channels and the formation of a stagnation layer due to the collision of the two plasmas. The dissipation of the stagnation layer into its nearby space in the third stage can be clearly observed in the images. Applying the 1-D model, the simulation results predict the temperature spikes and density increase in the layer due to the conversion of the macro-kinetic energy of the plasmas into their internal energy with the flow velocities almost vanishing. The ratios of the ion–ion mean-free-path to the characteristic length at the midpoint of the two plasmas, extracted from the simulation, indicate that the stagnation layer is a soft one with partial plasma interpenetration through the interface between the two plasmas. [ABSTRACT FROM AUTHOR]

Forward stimulated Raman scattering and backward stimulated Raman scattering (BSRS) are measured when an intense 532 nm nanosecond pulsed laser is focused into water and heavy water. The investigation reveals a significant observation: the formation of the ice VII structure exclusively occurs in the backward direction when optical breakdown takes place, provided that the input energy falls below 90 mJ for liquid water or 75 mJ for heavy water. This phase transition is attributed to secondary shock compression, which comes from energy transfer and compression between the BSRS in plasmas with the pump laser. The optical breakdown experiment under pre-pressure reveals that the shock compression in the back direction is approximately 2.3 times that of the forward direction. This research is useful for shock compression and dynamics in plasmas. [ABSTRACT FROM AUTHOR]

The evolution of filaments due to the Weibel Instability was studied through experiments of two asymmetric counterstreaming plasmas produced by nanosecond laser pulses with total energy more than 1 kJ. The magnetic field around filaments was measured by the Faraday rotation technique as tens of Tesla after an exponential growth at the rate of 0.148 ns − 1 , which was in good agreement with the calculated features of the Weibel Instability with experimental plasma properties. The temporal evolution of the separation distances between filaments was also recorded and fitted with two analytical models by Medvedev et al. [Astrophys. J. 618, L75–L78 (2005)] and Ruyer et al. [Phys. Plasmas 22, 032102 (2015)], respectively. While the magnetic field growth followed the quasi-linear theory of the Weibel Instability process in counterstreaming plasmas of non-relativity, the evolution of filaments through coalescence behaviors presented a nonlinear temporal increase in the filament widths. [ABSTRACT FROM AUTHOR]

Self-generated magnetic field and electron jet are observed when ultra-intense lasers (> 1 × 10 18 W / c m 2 ) interact with plasma. It is found that the self-generated magnetic field plays a significant role in the generation of electron jets. The generation mechanism of electron jets under the influence of a self-generated circular magnetic field is examined. It is revealed that magnetic modulation of self-generated magnetic fields can result in the collapse of these fields, consequently leading to the production of electron jets. Furthermore, it has been discovered that the velocity of the electron jets is associated with the maximum growth rate of the modulational instability. As the maximum growth rate of the modulational instability decreases, the velocity of the electron jets is reduced. The present work aids in getting a deeper understanding of the generation of electron jets in relativistic laser plasmas. [ABSTRACT FROM AUTHOR]

The interplay between ultrafast laser focusing conditions, emission intensity, expansion dynamics, and ablation mechanisms is critical to the detection of light isotopes relevant to nuclear energy, forensics, and geochemistry applications. Here, we study deuterium ( 2 H α) emission in plasmas generated from femtosecond laser ablation of a Zircaloy-4 target with a deuterium concentration of ≈ 37 at. %. Changes in emission intensity, plume morphology, crater dimensions, and surface modifications were investigated for varying focusing lens positions, where the laser was focused behind, at, and in front of the target. Spatially resolved optical emission spectroscopy and spectrally integrated plasma imaging were performed to investigate emission spectral features and plume morphology. Laser ablation crater dimensions and morphology were analyzed via optical profilometry and scanning electron microscopy. The 2 H α emission intensity showed significant reduction at the geometrical focal point or when the focal point is in front of the target. For all laser spot sizes, a two-component plume was observed but with different temporal histories. At the best focal point, the plume was spherical. When the laser was focused behind the target, the plume was elongated and propagated to farther distances than for the best focal position. In contrast, when the laser was focused in front of the target, filaments were generated in the beam path, and filament-plasma coupling occurred. By focusing the laser behind the target, the amount of material removal in the laser ablation process can be significantly reduced while still generating a plasma with a sufficient 2 H α emission signal for analysis. [ABSTRACT FROM AUTHOR]

The mechanism of double-pulse laser irradiation under spatial confinement remains unclear due to complex plasma plume dynamics and multiple shock wave interactions. In this study, coupling of spatial confinement and double-pulse irradiation was investigated using fast photography, laser shadowgraphy, and spectroscopy. The experimental results demonstrated unique dynamic processes of plasma plume and shock waves, confirming that the plasma plume was eventually reshaped into a jet-like structure, and the combined enhancement effect can be regulated through different parameters, including inter-pulse delay and plate spacing. The inter-pulse delay dictates the primary mechanism of the secondary pulse's interaction with the initial plasma and the target surface; as it increases, plasma front absorption decreases while target surface ablation intensifies. Plate spacing determines the delay from laser incidence to plasma plume compression; along with the inter-pulse delay, it influences whether the secondary pulse generates a second-generation shock wave that merges with the initial shock wave for compression or performs a secondary compression after the first. Compared to double-pulse irradiation alone, combined enhancement increased emission intensity of Fe, Ni, and C spectra by up to 4.1 times accompanied by the increase in plasma temperature. The R2 of calibration curves was increased, and the sensitivity for trace components Cr and C was improved with limits of detection reaching 255 and 659 ppm. [ABSTRACT FROM AUTHOR]

As nanophysics constitutes the scientific core of nanotechnology, it has a decisive potential for advancing clean renewable energy applications. Starting with a brief foray into the realms of nanophysics' potential, this review manuscript is expected to contribute to understanding why and how this science's eruption is leading to nanotechnological innovations impacting the clean renewable energy economy. Many environmentally friendly energy sources are considered clean since they produce minimal pollution and greenhouse gas emissions; however, not all are renewable. This manuscript focuses on experimental achievements where nanophysics helps reduce the operating costs of clean renewable energy by improving efficiency indicators, thereby ensuring energy sustainability. Improving material properties at the nanoscale, increasing the active surface areas of reactants, achieving precise control of the physical properties of nano-objects, and using advanced nanoscale characterization techniques are the subject of this in-depth analysis. This will allow the reader to understand how nanomaterials can be engineered with specific applications in clean energy technologies. A special emphasis is placed on the role of such signs of progress in hydrogen production and clean storage methods, as green hydrogen technologies are unavoidable in the current panorama of energy sustainability. [ABSTRACT FROM AUTHOR]

Traditional mechanical processing of zirconium leads to an unfavorable transformation, from a metastable tetragonal phase to a monoclinic phase (t→m), which weakens the structure of the material and subsequently leads to damage to the prosthetic restoration. The aim of this research is to compare commonly used surface treatments to determine which has the least effect on t→m. Thirty cylindrical samples made of sintered zirconium were divided into six groups based on the following treatments: polishing, grinding, sandblasting, chemical etching, laser structuring or dry plasma etching. After surface treatment, the samples were subjected to the following tests: X-Ray Diffraction, microscopic examination, surface wettability and surface roughness measurements. Chemical etching, laser structuring and plasma etching significantly reduce the content of the monoclinic phase. All surface treatments significantly reduced the final amount of the monoclinic phase. However, chemical etching did not provide sufficient surface roughness. Both laser and plasma processing offer the advantage of creating structural patterns on the surface of elements. However, as plasma etching requires a mask to obtain the appropriate pattern on the surface, it seems that laser processing offers more and varied structuring possibilities. Laser structuring is easier to control and more economical than the other methods. [ABSTRACT FROM AUTHOR]

This study investigates the optical properties of yttrium ferrite thin films fabricated via pulse laser deposition. Yttrium orthoferrite, a ferrimagnetic material known for its potential applications in spintronics and photonics, was deposited on single-crystal substrates under controlled conditions to analyze its optical characteristics. The influence of deposition time on the film quality and optical properties was examined. Atomic force microscopy in contact mode revealed surface roughness variations up to 35 nm, indicating the films' ability to cover substrate defects. Reflectance measurements determined the optical band gap, which decreased from 3.17 eV for thinner films (44 nm) to 2.91 eV for thicker films (93 nm). Forbidden electronic transitions were also observed, attributed to heteroepitaxial growth and phonon interactions. These results demonstrate the effect of film thickness on morphology and optical properties, making YFeO3 films promising for a range of optoelectronic applications. [ABSTRACT FROM AUTHOR]

As part of the work on creating an x-ray microscope, experimental and theoretical studies of laser plasma of solid copper targets in the soft x-ray range were carried out. With a laser pulse duration of 2.5 ns (FWHM), the power density of the Nd:glass laser on the target is varied in the range 0.8 × 1013–4.2 × 1013 W/cm2. Experimental results demonstrated the presence of intense plasma emission in spectral ranges of water and carbon windows, and the number of photons of the most intense lines was calculated. Spatio-temporal studies of copper plasma have demonstrated intense emission in the wavelength range shorter than 15 Å, and the images of plasma emission in time-integrated and linear sweep modes are shown. The simulations of the interaction of the specified laser radiation flux with copper targets were carried out taking into account the transfer of self-radiation in plasma. The non-local thermodynamic equilibrium optical properties of the plasma were used. As a result of calculations, profiles of density, temperature, electron thermal conductivity flux, emissivity of plasma, and self-radiation flux were obtained. The calculated spectrum of the outgoing radiation is consistent with that obtained at the experiment. [ABSTRACT FROM AUTHOR]

Accelerated diagnostic of plasma plays a significant role in controlling and optimizing plasma-mediated processing, particularly for plasma with higher temporal and spatial gradients, such as laser produced plasma (LPP). In the present work, two advanced machine learning (ML) algorithms, random forest regression, and gradient boosting regression are integrated with noninvasive collisional radiative (CR) model-based optical diagnostics to facilitate accurate diagnostics. A comprehensive fine-structure resolved CR model framework is developed by incorporating our consistent cross section data obtained from the Relativistic Distorted Wave method [Suresh et al., "Fully relativistic distorted wave calculations of electron impact excitation of gallium atom: Cross sections relevant for plasma kinetic modelling," Spectrochim. Acta B: At. Spectrosc. 213, 106860 (2024)]. An extensive dataset of CR model simulated intensities is created to train and test the ML methods. The present CR model is applied to characterize the Gallium LPP coupling with the optical emission spectroscopic measurements of Guo et al. ["Time-resolved spectroscopy analysis of Ga atom in laser induced plasma," Laser Phys. 19, 1832–1837 (2009)] at different delay times. Further, a detailed correlation study of the line intensity ratios is performed to observe the qualitative behavior of the plasma parameters. The electron temperature results obtained from the CR model, ML, and line ratio methods were compared and found to be in excellent agreement. Overall, the present study demonstrates diagnostic approaches that can benefit the LPP community significantly by providing a rapid understanding of the plasma behavior across various operating conditions. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is a promising technique to monitor carbon emissions in post-combustion flue gas. However, its measurement accuracy is susceptible to variations in gas temperature. In this work, a mid-level data fusion method integrating spectral and acoustic signals generated by laser-induced plasmas (LIPs) was proposed to improve the measurement accuracy. This method utilizes the high sensitivity of acoustic signals to variations in gas temperature, enabling a correction of temperature effects. The acoustic features were extracted from both the time-domain waveforms and frequency spectra, while the spectral features were selected using a SelectKBest method. These features were fused into a new array, on whose basis multivariate regression models including Partial Least Squares (PLS), Support Vector Machines (SVM), and Random Forest (RF) were trained. Data fusion significantly improved the predictive precision and trueness of SVM and RF models, with the RF model achieving the best performance: a coefficient of determination (R2) of 0.9941, a root-mean-square error (RMSE) of 0.4864, a mean absolute error (MAE) of 0.2587, and a mean absolute deviation (MAD) of 0.0980. Shapley additive explanation (SHAP) analysis revealed that in the RF model, the acoustic features that exhibited higher temperature sensitivity could be more frequently selected in the training process and thus had greater impacts on model outputs, which can better correct for the gas temperature effect. Furthermore, the potential of this method in industrial applications was demonstrated in an unsteady flow. [ABSTRACT FROM AUTHOR]

The storage and management of nuclear waste materials require the detection of uranium, but traditional analytical methods are unsuitable for radioactive environments. The enhancement methods of uranium in glass matrices using fiber-optic laser-induced breakdown spectroscopy are still underdeveloped. Using an optical diagnostic system coupled with fast photography, shadowgraphy, and optical emission spectroscopy, the evolution of laser-induced plasma generated from a glass matrix under spatial confinement is studied. The plasma evolution image illustrates the temporal consistency between the compression of plasma width and the enhancement of luminescence intensity. Two enhancements were observed when the plate spacing was smaller than the plasma, which might be due to the high density of the core plasma or a synergistic effect of plasma expansion and shockwave confinement. Under spatial confinement, there is a 3–4-times enhancement in the intensity of uranium spectral lines and a 2–4 times enhancement in the signal-to-noise ratio. Several calibration curves are established under spatial confinement based on U II 409.01 nm, U II 367.01 nm and U I 358.48 nm. The lowest limit of detection (LOD) of uranium reaches 95 ppm, which supports the application of FO-LIBS in the detection of uranium-containing nuclear waste materials. [ABSTRACT FROM AUTHOR]

In this investigation, a spectroscopic optical emission test was used to investigate the characteristics of gold plasmas that were produced in the surrounding environment using an Nd: YAG system at a wavelength of 1064 nm and had an energy output that varied from 400 to 600 mJ. The emission spectrum profiles of (Au) were analyzed and recorded using a spectrometer to aid in the extraction of vital plasma features (i.e., T e and n e ). Plasma temperature was determined using the Boltzmann plot method, and electron density was determined using the Stark broadening method. The temperature was between (0.91 and 0.94) eV, while the electron density ranged between (4.79 and 5.26) × 1 0 1 7 cm − 3 . The rest of the plasma parameters were calculated by the mathematical equations of the method used (Boltzmann Plott). [ABSTRACT FROM AUTHOR]

In this study, we have investigated the relationship between the plasma temperature in remote laser-induced breakdown spectroscopy (LIBS) experiments and the hydrophobic properties of silicone rubber insulators (SIRs). Contact angle and LIBS measurements were conducted on both artificially-aged (accelerated aging) and field-aged SIRs. This study reveals a clear connection between plasma temperature and the properties of aged SIRs on artificially-aged SIR specimens. Specifically, the plasma temperature exhibits a consistent increase with the duration of the accelerated aging test. The hydrophobicity of the artificially-aged SIRs was assessed by performing contact angle measurements, revealing a decrease in the hydrophobicity with increased aging test duration. Furthermore, we extended our investigation to the study of nine field-aged SIRs that had been in use on 150 kV overhead transmission lines for 0 to 21 years. We find that the laser absorption and hardness of the material do not relate to the plasma temperature. In summary, we observe a direct connection of plasma temperature to both contact-angle measurements and operation time of the in-service insulators. These results strongly suggest the potential use of LIBS for remotely evaluating the hydrophobicity and aging degree of silicone rubber insulators, thus assessing their real-time on-site operational quality. [ABSTRACT FROM AUTHOR]

A helium (He) atmospheric pressure plasma jet (APPJ) system with a single electrode was configured. A pulsed light of femtosecond (fs) laser was irradiated at the guided streamer of He APPJ through an objective lens to generate the laser induced plasma (LIP) inside the He APPJ. The optical emission spectra of LIP were measured as the light energy of the fs laser increased. The spectra of hydroxyl molecules and atomic oxygen were enhanced when the fs laser energy exceeded 114 μJ. The plasma parameters of LIP inside the APPJ were determined using He collisional-radiative model. Electron temperature and density increased to ∼ 7.2 eV and 1.7 × 10 14 cm − 3 , respectively. The dominant processes underlying the enhancement were discussed in the interaction of fs laser and He APPJ. [ABSTRACT FROM AUTHOR]

The role of the density gradient in the electron acceleration process by intense laser pulses for a plasma profile with a steep interface between vacuum and a strongly overdense plasma is investigated via particle-in-cell simulations with the Emi2d code. Laser pulses at relativistic intensities interacting with finite gradients at the laser–plasma interface favor collective electron motion in the underdense plasma provided that the pulse duration is long enough to form a standing wave structure. It is shown that the steepness of the gradient influences the evolution of the distribution of electrons that are injected into the dense plasma. Heating mechanisms of the electron bulk and a very energetic electron tail are identified. The heating of the targets evolves each time when bunches of electrons accelerate to relativistic energies and return to the laser–plasma interface. The heating dynamics have consequences on the ion front motion at the rear of the target. This is elaborated by determining the predominant hot electron populations and their temperatures that govern the expansion of the rear density profile. The role of the temporal dynamics of the hot electron populations is investigated with respect to the known analytic models for ion acceleration at the rear target, showing that those models are robust despite the important temporal increase in hot electron temperatures. [ABSTRACT FROM AUTHOR]

Magnetic reconnection is a ubiquitous fundamental process in space and astrophysical plasmas that rapidly converts magnetic energy into some combination of flow energy, thermal energy, and non-thermal energetic particles. Over the past decade, a new experimental platform has been developed to study magnetic reconnection using strong coil currents powered by high-power lasers at low plasma beta, typical conditions under which reconnection is energetically important in space and astrophysics. KJ-class lasers were used to drive parallel currents to reconnect MG-level magnetic fields in a quasi-axisymmetric geometry, similar to the magnetic reconnection experiment or MRX, and thus this platform is named micro-MRX. This presentation summarizes two major findings from micro-MRX: direct measurement of accelerated electrons and observation of ion acoustic waves during anti-parallel reconnection. The angular dependence of the measured electron energy spectrum and the resulting accelerated energies, supported by particle-in-cell simulations, indicate that direct acceleration by the out-of-plane reconnection electric field is at work. Furthermore, a sudden onset of ion acoustic bursts has been measured by collective Thomson scattering in the exhaust of magnetic reconnection, followed by electron acoustic bursts with electron heating and bulk acceleration. These results demonstrate that the micro-MRX platform offers a novel and unique approach to study magnetic reconnection in the laboratory in addition to the capabilities provided by traditional magnetized plasma experiments such as MRX and the upcoming Facility for Laboratory Reconnection experiments (FLARE). Future prospects to study other particle acceleration mechanisms and ion acoustic waves from magnetic reconnection are also discussed. [ABSTRACT FROM AUTHOR]

In this work, we present a study aimed at the statistical distribution of characteristic signals of laser-induced plasmas. This work mainly focuses on observing statistical distribution for repetitive measurement of spectra, plasma plume imaging, and sound intensity. These were captured by using various laser irradiances, spanning between 1.72 and 6.25 GW cm-2 for a 266 nm laser. Their distributions were fitted by Gaussian, generalized extreme value (GEV), and Burr distributions, as typical representation models used in LIBS. These were compared using the Kolmogorov-Smirnov (KS) test by its null hypothesis on whether these models are suitable or fail to describe the statistical distribution of the data. The behavior of the data distribution has shown a certain connection to the plasma plume temperature. This was observed for all the used ablation energies. Performances of the statistical models were further compared in the outlier filtering process, where the relative standard deviation of the filtered data was observed. The results presented in this work suggest that an appropriate selection of a statistical model for the data representation can lead to an improvement in the LIBS performance. [ABSTRACT FROM AUTHOR]

Focuses on a study that described the enhancement of soft x-ray emission using prepulses with laser plasmas. Details of the study; X-ray generation efficiencies of gold targets; Dependence of the x-ray conversion efficiencies on the plasma-emitting volume.